This invention relates to liquid dispensing systems having vapor recovery means such as are employed in automobile service stations where fuels are dispensed from storage tanks to receptacle tanks on vehicles and vapors from the vehicle receptacle tanks are withdrawn from the tanks and the surrounding atmosphere and are returned to the storage tank. Vapor recovery systems may be classified in two categories, namely, balanced pressure systems and vacuum assist systems. In the former, a sealing arrangement such as an elastomeric boot is provided which engages the vehicle fill pipe during fueling operations in sealing relationship. The interior of the boot is connected through a vapor return conduit to the underground storage tank and by this means, vapors forced out of the vehicle tank as it is filled are returned to the storage tank where they are largely recovered.
The vacuum assist system differs from the balanced pressure system in that in the vacuum assist system no sealing arrangement with the fill pipe is provided. Instead, conduit means associated with the dispensing nozzle and connected through a vacuum pump or other vacuum inducing means, are employed to collect vapors emerging from the vehicle tank and from the vicinity of the fill pipe and conduct them through a conduit back to an appropriate storage tank, thus effecting recovery of the fuel and preventing atmospheric pollution.
The dispensing nozzle of the present invention has particular utility when utilized in a vacuum assist system. Such a system is described in U.S. patent application Ser. No. 36,302 of Donald C. Walker et al. for "Vapor Recovery System and Nozzle" filed May 7, 1979 and assigned to the same assignee as the present application. U.S. patent application Ser. No. 36,302 is hereby incorporated by reference. In this application the vacuum for aspirating the vapors from the vehicle tank and vicinity is preferably provided by a pump which is driven by an hydraulic motor actuated by fuel flowing through a service station dispensing unit. A somewhat similar arrangement is disclosed in U.S. Pat. No. 3,913,633 to Hiller. Hiller discloses a vacuum assist system in which an injector is used to create a vacuum in response to the dispensing of liquid from the storage tank. U.S. Pat. No. 3,826,291 to Steffins discloses a vacuum assist system in which the vacuum is provided by a vapor pump driven by the shaft of the meter which operates an indicator of the amount of liquid dispensed. U.S. Pat. No. 4,058,147 to Stary et al. discloses a vacuum assist system in which a motor driven vapor pump is employed to produce a vacuum at the dispensing nozzle. A means, responsive to the flow of liquid through the nozzle, to automatically open a vapor valve to an extent proportional to the rate of liquid flow through the nozzle is provided.
U.S. Pat. No. 4,286,635 to McMath discloses a dispensing nozzle for use in a balanced pressure type system. The McMath nozzle has a vacuum tube disposed within the central portion of the nozzle spout for sensing the presence of liquid in the fill pipe when the tank is filled. When this tube is blocked by liquid, diaphragm means actuate a shut-off valve to cut off liquid flow. McMath also has a diaphragm operable in response to pressure within the vehicle tank to shut off liquid flow when a predetermined tank pressure is exceeded. This latter feature is, of course, not useable in vacuum assist type systems which do not have a seal formed between the nozzle and the vehicle tank fill pipe. The McMath patent is also of interest in that it discloses a means for sealing the vapor return conduit from the atmosphere when the nozzle is not in use. In McMath a retainer ring on the nozzle spout is adapted to engage an elastomer sealing on the end of the vapor return boot when the spout is not received in the fill pipe.
U.S. Pat. No. 4,276,916 to Ostand discloses a dispensing nozzle for a balanced pressure type system similar to McMath but having a float in the vapor return conduit responsive to the presence of a predetermined quantity of liquid which causes an actuator or transducer to be activated to shut off liquid flow through the nozzle in the event the vacuum tube within the spout should fail to function and stop the flow.
In an effective vacuum assist type vapor recovery system the following requirements must be met:
(1) The conduit for conducting liquid from the storage tank to the dispensing nozzle must be sealed closed except when liquid fuel is being pumped. PA1 (2) This conduit also must be closed to stop the pumping of liquid when the vehicle tank is filled to a predetermined level to prevent spillage on the ground. PA1 (3) The vapor return conduit from the nozzle back to the storage tank or other collection point must be open when liquid is being pumped into the vehicle tank and must be sealed closed when liquid is not being dispensed and a partial vacuum is not present in this conduit. PA1 (4) Liquid must not be aspirated into the vapor return conduit from the vehicle tank or fill pipe or from other parts of the nozzle. Otherwise customers would be charged for fuel which was aspirated back to the storage tank after having passed through a registering dispenser. PA1 (a) a nozzle body having an inlet and an outlet for liquid to be dispensed; PA1 (b) a filling spout attached to the nozzle body adapted for loose fitting reception in a vehicle tank fill pipe and having an internal conduit for liquid connecting to the body outlet and an external conduit for vapor return surrounding the liquid conduit, the two conduits defining an annular passage for conducting vapor from the vehicle tank to a vapor return conduit means in the nozzle body; PA1 (c) a valve in the body for controlling the flow of liquid through said body from said inlet to said outlet; PA1 (d) a manually operated means for controlling the operation of the valve and vacuum responsive release means to allow closing of said valve and stoppage of liquid flow when a predetermined partial vacuum is induced within the nozzle body; PA1 (e) venturi means responsive to liquid flow through the body for inducing a partial vacuum and an interconnecting passage between the vapor return conduit means to the venturi means normally allowing the flow of vapor from said vapor return conduit means to said venturi means to limit the partial vacuum induced thereby and said interconnecting passage being located at a point in the vapor return conduit which becomes full of liquid at such times when liquid begins to be aspirated from the vehicle tank through the vapor return conduit; and PA1 (d) a check valve within the nozzle body for closing the vapor return conduit valve which is actuated to the open position by liquid pressure within the nozzle body when the control valve in the nozzle body is open.
A large majority of the dispensing nozzles now in use employ a vacuum sensing line within the spout of the kind shown and described in U.S. application Ser. No. 36,302 as well as in the McMath and Ostand patents described above. The use of such an arrangement has several disadvantages. For example, splashing liquid may momentarily block the vacuum line causing actuation of the shut-off mechanism and premature shut-off before the vehicle tank is filled. Moreover, as pointed out by Ostand (Column 1, lines 34-35), in a vapor recovery system it is not always certain that the shut-off means will function to prevent liquid flow through the vapor return conduit because of faulty positioning of the spout in the fill pipe. Another disadvantage of the vacuum sensing line in the spout arrangement, particularly in vacuum assist system such as that described in Ser. No. 36,302 where the annular vapor return conduit is disposed within the spout, is that the vacuum sensing line occupies volume within the inner conduit and impedes liquid flow. In this connection it should be noted that the current arrangement in which "lead restrictor" plates are installed in fill pipes of vehicles equipped with catalytic converters limits the outer diameter of the spout and this in turn limits the diameter of the inter spout conduit.
A principal object of the present invention is to provide a foolproof dispensing nozzle satisfying all of the requirements enumerated above and which does not employ a vacuum sensing conduit within the fuel passage of the spout.
Another object is to provide a system which is hydraulically and pneumatically actuated deriving the power to actuate the various elements from the fluid streams.